A radar system typically includes an array of transmit and receive modules/elements, which may be referred to as radiator fins, electrically coupled to an array of associated integrated microwave circuits. Typically, each radiator fin is coupled to an associated integrated circuit by a combination of an electrical channel through an interconnect. Although radar systems typically operate in the X to K band at a frequency on the order of 10 to 35 gigahertz, in some applications it may be desirable to operate a radar system at higher operating frequencies. To operate a radar at high frequencies, however, the radar must include a greater number of radiator fins per square inch. Accordingly, the size of components within the radar system must be decreased.
The length of the interconnect coupling each radiator fin to an integrated circuit, however, is a limiting factor in the development of high frequency radar systems as very low inductive interconnections between devices important for high-frequency applications. Since flip chips have short bond connections between the active integrated circuit and the surrounding substrate, flip chip techniques have been used to combat this problem. Flip chips, however have their disadvantages. Microwave flip chip dies require embedded micro-strip or co-planar wave guide transmission lines to interconnect the passive elements on a semiconductor die to achieve the design function. This results in complex fabrication process and/or compromise in performance. Further, the bumps formed on the surface of the integrated circuit to bond the flipped integrated circuit to the substrate are expensive to form and require complex assembly techniques. Additionally, because coolant flow used to dissipate heat from an integrated circuit is removed from the semiconductor surface in a flip chip design, radar systems incorporating flip chips have thermal failure problems resulting from the inefficiency and inability of the active device to dissipate heat. Complex cooling systems, incorporating thermal bars within the semiconductor die, are needed for flip-chip packages. High operating temperatures result in reduced performance of the flip chip and the substrate supporting the flip chip.